Airplane Range on 100 EC

[18Watt]

1 hour ago, camacju said:

Have you tried further reducing motor size? A smaller motor would have less weight and draw less power. You'd need to have a higher torque limit, but that is likely a good thing - it gives you finer control over your overall torque.

This is one thing I haven't seen @OJT do.  Not that he hasn't done it, just hasn't specified it in his (excellent) summaries.  Normally, I don't consider this to be a huge benefit, but you've seen the vessels I create- clunky at best.  However, I do normally 'downsize' the motors to represent the max torque (or power) I'll ever need for a given vessel.  Yes it's true, the weight savings are not earth-shattering.  I do it more for a 'just because' mindset, I don't need that much available power, so I scale it back.

For @OJT and @camacju, I suspect every gram of optimization is beneficial.

1 hour ago, camacju said:

Interestingly enough, single blade propellers do exist in the real world:

Again, I have not tried this.  Not sure how KSP reacts to a single prop blade.  It seems absolutely un-practical.  But, if either of you is seeing better performance with less blades, it might be worth at least testing.  Actually, @OJT reported that he's using more than two blades per rotor.  With GREAT success, I should add.  But that was a funny photo.  Just a guess, but I suspect that originated when an owner discovered unrepairable damage to a blade.  Instead of buying a new prop, hey why not chop off the bad blade, add some lead, and see how it works?

Boy howdy, you guys have taken this challenge way beyond what I originally envisioned.  My hat is off to both of you!

If I could only convince you guys to make an Elcano entry!  Just kidding, it's a really time-consuming endeavor...

 

[camacju]

Okay, this is getting ridiculous. My power usage is so low that KSP flatly refuses to tell me the motor is drawing any power at all.

In fact, after a full minute, KSP tells me that less than 0.01 units of electric charge have been used.

Doing some quick back of the napkin math:

Assume 0.01 electric charge used per minute (Upper bound of what's actually possible given my readouts)

9974 minutes * 60 seconds * 55.6 m/s = 33273 km

The problem is that this will take a full week to actually finish! My computer probably can't go that long without blue screening. So this is firmly in the realm of a theoretical mission.

Increasing the throttle a little bit, finally I start to see some power draw! Each motor is drawing 1.03 milli-units per second, or 2.06 milli-units per second (0.00206 u/s) in total.

This translates to a flight time of 48252 seconds, or about 13 hours. This is actually pretty reasonable, but still far too long for me.

This also implies a max range of 3339 km. A full circumnavigation of Kerbin is 3768 km. It's tantalizingly close!

Edited May 18, 2022 by camacju

[18Watt]

25 minutes ago, camacju said:

This also implies a max range of 3339 km. A full circumnavigation of Kerbin is 3768 km. It's tantalizingly close!

Jeepers.  The image of the 100 EC battery pack looks like two D-cells in a holder.

I realize y'all are pushing the limits (to say the least..).  However, at this point, I don't see anything I'd consider a 'cheat' or 'exploit'.  Near as I can tell, you and @OJT are just optimizing how KSP calculates thrust, drag, and EC usage.

I believe you mentioned that some exploits have been eliminated from the game, like the 'infiniglide' thing.  Would either of you describe what you're seeing as 'cheats' or 'excessive exploits'?  By that I mean creating energy from basically nothing.  Again, so far I'm not really seeing anything 'cheaty', you are simply optimizing your vessels to the physics rules of KSP.

I do understand why some challenges limit optimization- it doesn't always reflect what is possible in real life.  This challenge is not about that- The idea is if KSP will allow you to do something, how far can you take those limitations?  However, I do want to avoid getting into 'infiniglide' territory.  Again, so far I'm not seeing energy created out of nothing- just optimization.  Let me know if y'all are seeing things that get into 'cheaty' territory though.

As an Elcano veteran, even I would have to think hard before attempting to do a Kerbin circumnavigation at 60 m/s.  Biggest concern: It's almost summer here where I live, I have stuff to do outside right now!  I can do KSP for an hour or so, but for a 12-hour circumnavigation session I'd need to wait till winter..

Unfortunately I can't add you to the leaderboard until the flight occurs.  Best I can do is make a note of what is theoretically possible.

[camacju]

And... we've finally done it!

I found that flying higher is actually beneficial, as I can fly faster for the same drag and thus the same motor output power. This only really breaks down when I start reaching Mach effects around the propeller, where I'll want to fly lower to take advantage of the higher speed of sound. However, Mach effects are insignificant here.

0.00204 electricity used per second. 95.48 / 0.00204 * 84.6 = 3960 km.

Just now, 18Watt said:

Would either of you describe what you're seeing as 'cheats' or 'excessive exploits'?  By that I mean creating energy from basically nothing

I wouldn't describe anything I'm currently doing as a cheat. I'm not taking advantage of any magic wing effects - in fact, I'm doing the opposite, as I'm flying at a -1 degree AoA right now and so I actually get a penalty from fairing body lift.

The props aren't spinning infinitely and in fact take a positive torque to maintain. They're slightly offset inward, but I'm not generating any phantom torque. 

I don't know what happened with the zero power draw, but it felt a bit too cheaty for me, so I purposely increased torque limit in order to draw a measurable current.

[18Watt]

Just now, camacju said:

I found that flying higher is actually beneficial,

I'll sleep better now!  Seriously.

You, and especially @OJT, have (up to now) achieved increasing gains by flying much lower than what I had expected would be 'ideal'.  I can't help but think that things have to get better in thinner air.  That hasn't been the case yet- until your last post..

[18Watt]

4 minutes ago, camacju said:

I don't know what happened with the zero power draw, but it felt a bit too cheaty for me, so I purposely increased torque limit in order to draw a measurable current.

I suspect rounding errors, or a similar phenomenon is happening.  I find it helpful to keep in mind that for really small values, what is displayed is not necessarily what is actually occurring.  On the other hand, at that point it's worth asking, "if KSP can't display current draws that low, is it actually dinging the battery at all?"

Y'all are keeping a ~1,000 kg craft housing two Kerbals aloft for a nearly indefinite period!  Fuselage drag notwithstanding, it still costs energy to generate lift, and counteract parasitic drag.

When you reach the point where you can't tell if the battery is being depleted or not (and I think we're there...), I imagine it becomes difficult or impossible to make methodical improvements.  How do you know if you're doing better than the last run?  The current draw is basically zero for both runs, so which one is doing better?

I really wish I could make some competitive entries, but I'm just not proficient at reducing drag.  Plus, I do like to 'set the bar low' when starting challenges to encourage participation- but in this case the entries have wildly eclipsed what I could have come up with.

[camacju]

19 minutes ago, 18Watt said:

I suspect rounding errors, or a similar phenomenon is happening.  I find it helpful to keep in mind that for really small values, what is displayed is not necessarily what is actually occurring.  On the other hand, at that point it's worth asking, "if KSP can't display current draws that low, is it actually dinging the battery at all?"

Actually I'm almost certain that KSP was simply rounding the current down to zero. Right now I'm at 4% thrust limit and drawing about 0.01 units of charge every 5 seconds. Meanwhile, in my earlier picture, I was at 3% thrust limit, which meant I should have expected to draw 0.01 units of charge every 7-8 seconds. But I went a full minute and didn't see any current draw.

Small update:

I'm over the continent where my last mission landed. I'm actually still increasing speed slightly, so this next estimate is again an underestimate of the maximum range of this craft.

91.89 / 0.00206 * 89.8 = 4006 km remaining. 

Maybe we could have an alternate leaderboard for using only ten units of electric charge?

Edited May 18, 2022 by camacju

[camacju]

One final update before I go to sleep:

20 electric charge used. Around 81 degrees of longitude have been covered. That's about 848 km.

Total estimated range is now 4241 km. The craft seems to be perfectly stable at this height and speed, so I think I'll go to sleep and see where it's at when I wake up.

Hopefully my computer doesn't crash.

[OJT]

5 hours ago, 18Watt said:

This is one thing I haven't seen @OJT do.  Not that he hasn't done it, just hasn't specified it in his (excellent) summaries.

Both 1000 and 2000km entries used 20% sized small motor. Reducing the motor size to 1% saves me 7 kilos, which doesn't really make much impact

However, I noticed what DOES make a huge impact: fan blade offsetting. Offsetting them inwards, so they make a smaller circle, noticeably increases thrust while consuming less charge. My calculated theoretical ranges exceed 4500 kilometers by now, which is more than enough to make a circumnavigation

From what I read, @camacju also did prop offsetting in his latest screens. It seems, after all, you can make a circumnavigator with 100 EC charge

[OJT]

I tested this directly after my 2000+km entry

The very same plane, only thing done is fan blade offsetting. 1.99 microunits per second max usage (compared to 3.48 microunits) and cruise speed of 92-98 m/s (compared to 69-75 m/s). Not taking into account the 2 EC used to get up to speed and taking the average speed as estimate, (98EC/0.00199units)*95m/s = 4678km of range

However, at this point the flight will take over 13 hours, and I already didn't feel comfortable leaving the game on for 8 hours in previous entry, so this is basically left as a thought experiment of sorts. But YES, you can circumnavigate on 100 EC

[swjr-swis]

7 hours ago, 18Watt said:

However, at this point, I don't see anything I'd consider a 'cheat' or 'exploit'.

I hate to be the party pooper, but yes, I would call this an exploit, because yes, there is absolutely free energy being created.

 

Proof, with a plane with a relatively poor cabin drag-optimization compared to the other two entrants. The only improvements it introduces are the better choice of wing part and a system to almost nullify the vibrations that kill SAS, allowing me to simply use SAS on ORB PRG to let the plane fly itself:

Two rotors set at max size/power and max RPM, with two of the smallest duct fan blades each, liberally offset inward from their default to clearly show what's happening. Used all my EC simply getting up to speed and in the air. This was hands-off, ZERO management of blade deployment, rotor torque, or RPM limit - all I did was release the brakes.

25 mins later, the plane is still at (over!) max RPM and climbing, 79.5 m/s at almost 9 km altitude. I didn't feel it necessary to wait a day to see  if it will circumnavigate because obviously it will. And being completely stable in flight, it doesn't even need watching.

Just to make sure, this time I went and LOCKED the battery just after take off.

Same result. Plane will keep going as if nothing's up and will obviously do so indefinitely. I have literally done nothing but close the fore bay, set SAS to ORB PRG, and released the brakes, zero prop/rotor management or even flying.

Let me be clear: I am a strong proponent of Applied Engineering in KSP, and I have zero issue with putting this to good use. But let's call it what it is: what we're seeing in this exchange is really just 'infini-props'. We can pretend it's not, but it's really just about how far we dare offset the prop blades inwards, allowing an arbitrarily low EC usage to keep up torque, passing through literal zero, and  then even becoming 'negative' since now the blades are basically creating their own torque (once the craft gains a bit of speed).

Craft file for anyone wishing to peer review: https://www.dropbox.com/s/eit1qdj09wf412c/SWiS TinyProp 3.craft?dl=0

 

 

Edited May 18, 2022 by swjr-swis
forgot to link the craft file

[michal.don]

1 hour ago, swjr-swis said:

Same result. Plane will keep going as if nothing's up and will obviously do so indefinitely. I have literally done nothing but close the fore bay, set SAS to ORB PRG, and released the brakes, zero prop/rotor management or even flying.

I have to admit, I have no experience in regards to atmo/phantom force exploits in the game  (I usually just build rockets  ). Could somebody please briefly explain what's going on here and how that works? If that's deemed as hijacking the challenge thread, I apologize and will ask the question in a different thread.

Michal.don

[swjr-swis]

43 minutes ago, michal.don said:

I have to admit, I have no experience in regards to atmo/phantom force exploits in the game  (I usually just build rockets  ). Could somebody please briefly explain what's going on here and how that works?

 

@camacju explained it ealier in this thread:

On 5/15/2022 at 3:56 AM, camacju said:

The propeller is completely off, but a phantom torque force is causing my propeller to spin up. Basically autorotation on steroids.

It works because KSP calculates propeller blade lift at a point offset way out from the axis of rotation to compensate for Unity's rotation limit. But lift also comes with a lift-induced drag acting opposite to the motion, which is applied at the base of the propeller.

Normally this is just fine, because the lift induced drag acts on the same side of the propeller as the lift point, causing a negative torque. But when the props are offset inward far enough, the drag acts on the opposite side of the propeller, which actually produces a positive torque.

This means that when the propeller produces thrust, the thrust induces a torque that further accelerates the propeller. So all I need to do is get the prop moving initially and then glide infinitely.

 

On regular lifting surfaces, all force vectors (drag/lift) act on the same point. On prop blades, the point of action for lift/thrust was moved somewhere far outside the tip of the blade to artificially enhance the generated thrust and make props more playable. In a default placement it works as expected, but when offsetting the blades inward the drag point moves to the opposite side while the lift point, being way out there, still stays in the 'correct' side. Instead of the airflow causing a drag that slows the props rotation, it's now accelerating the rotation, ie. magic torque that doesn't require rotor EC usage. Offset it enough and it becomes enough to not need any EC at all anymore, as long as there's an initial bit of airflow started.

 

[OJT]

3 hours ago, swjr-swis said:

I hate to be the party pooper, but yes, I would call this an exploit, because yes, there is absolutely free energy being created.

 

Proof, with a plane with a relatively poor cabin drag-optimization compared to the other two entrants. The only improvements it introduces are the better choice of wing part and a system to almost nullify the vibrations that kill SAS, allowing me to simply use SAS on ORB PRG to let the plane fly itself:

Two rotors set at max size/power and max RPM, with two of the smallest duct fan blades each, liberally offset inward from their default to clearly show what's happening. Used all my EC simply getting up to speed and in the air. This was hands-off, ZERO management of blade deployment, rotor torque, or RPM limit - all I did was release the brakes.

25 mins later, the plane is still at (over!) max RPM and climbing, 79.5 m/s at almost 9 km altitude. I didn't feel it necessary to wait a day to see  if it will circumnavigate because obviously it will. And being completely stable in flight, it doesn't even need watching.

Just to make sure, this time I went and LOCKED the battery just after take off.

Same result. Plane will keep going as if nothing's up and will obviously do so indefinitely. I have literally done nothing but close the fore bay, set SAS to ORB PRG, and released the brakes, zero prop/rotor management or even flying.

Let me be clear: I am a strong proponent of Applied Engineering in KSP, and I have zero issue with putting this to good use. But let's call it what it is: what we're seeing in this exchange is really just 'infini-props'. We can pretend it's not, but it's really just about how far we dare offset the prop blades inwards, allowing an arbitrarily low EC usage to keep up torque, passing through literal zero, and  then even becoming 'negative' since now the blades are basically creating their own torque (once the craft gains a bit of speed).

Craft file for anyone wishing to peer review: https://www.dropbox.com/s/eit1qdj09wf412c/SWiS TinyProp 3.craft?dl=0

 

 

That's what I was thinking about too

Without touching prop blades, the maximum distance you can go is roughly in 2000-2200 km range (and I did lots of testing to verify these numbers). Moving prop blades however creates these effects that both you and @camacju have described. Move them in far enough and they don't even need any electricity to spin by themselves, basically granting you infinite flight. But, does it make it viable to move the props in "just enough" that they still use charge? Like, camacju is getting theoretical ranges of 33 thousand kilometers for crying out loud

At this point, what constitutes a "legal" and "illegal" exploit? This whole challenge was pretty much dominated by aerodynamic exploits (with closing nodes and offsetting everything into the fairing and whatnot). And now we are at the point that the exploit is so strong that, if we use it too much, it goes into cheat reality, because you won't need any more charge to fly at all. So you're forced to scale it back intentionally so the engine still uses electricity. But how do you even optimize at that point? Even in-game telemetry gets confused and difference between 0.01 charge per 1 minute or 2 minutes can be in order of tens of thousands of km of range and how many more microns you move the prop inward

P.S. By the way, your wing structure is actually genius. How did I not think of that? 

Edited May 18, 2022 by OJT

[camacju]

Well, my computer didn't crash, but sometime during the night my frames dropped through the floor and I barely made any progress. Currently KSP is closed but I might try flying it some more today.

3 hours ago, swjr-swis said:

But let's call it what it is: what we're seeing in this exchange is really just 'infini-props'.

Not at all - I'm not offsetting the props enough for the torque flip to take effect. Instead, I'm simply reducing the radius of the propeller, reducing the torque needed to accelerate it up to speed. The same effect would occur in a real life propeller. There is no free energy.

The lift and drag points of the prop are still on the same side of the axis of rotation. Also the prop blades aren't clipped inwards into each other - they just appear to be attached end to end.

3 hours ago, swjr-swis said:

We can pretend it's not, but it's really just about how far we dare offset the prop blades inwards, allowing an arbitrarily low EC usage to keep up torque, passing through literal zero, and  then even becoming 'negative' since now the blades are basically creating their own torque (once the craft gains a bit of speed).

You've touched on the main reason why it's so hard to determine what counts as cheaty in KSP. Everyone has a different threshold for what mechanics they'll be willing to abuse, whether it be part clipping, root fairing body craft, magic wings, or even Kraken drives.

I think that offsetting the props one tick inward isn't too cheaty, as you aren't getting any torque reversal (No free energy) and thus the motor still requires some energy to operate. Again, the energy cost is reduced, but that matches the real world. Meanwhile, offsetting them further to create infini-props would be too cheaty for me as you're getting free energy. And it seems that you think any amount of prop offsetting is cheaty since you're reducing the required torque to drive the prop. I don't think there's any way to reconcile this without someone changing his (or her) opinion.

3 hours ago, swjr-swis said:

the better choice of wing part

Huh, I never realized that basic fins actually have a better mass ratio. Interesting, but this probably won't be useful for the SSTO craft I like because of the fin's terrible heat tolerance.

[swjr-swis]

18 minutes ago, camacju said:

The lift and drag points of the prop are still on the same side of the axis of rotation. Also the prop blades aren't clipped inwards into each other - they just appear to be attached end to end.

Barely. I think the regular drag force applies to the base of the blade or very near to it. At that point radial speed is minimal and so is the drag calculated for the blades = minimal torque required to get/keep them moving. Which is my point:

4 hours ago, swjr-swis said:

allowing an arbitrarily low EC usage to keep up torque, passing through literal zero

The optimization is based on moving the drag point to get as close to zero blade drag as one dares so the readouts still show a minimal EC usage and the divide-by-near-zero flight range goes through the roof. But since it's a continuous sliding scale, a micron more and it's now in infini-land.

Proof is in the pudding. I just exaggerated it to show the issue clearly, after you both stopped at the edge of it going into 'negative', while your previous series of entries show the range growing exponentially at the blades moving inwards.

[camacju]

4 hours ago, OJT said:

But how do you even optimize at that point?

There's still plenty of funky aerodynamics stuff to work with. For example there's a few different types of parts that can be used as "Magic wings," basically parts that can produce a higher lift to drag ratio than any of KSP's normal wings:

-Heat shields. These are the "standard" magic wing parts, but they're quite heavy and our ultra-low-power props will probably have a hard time getting them up to speed.
-Landing gear. These are slightly lighter than heat shields but have a lower lift to drag ratio. Also you can land on them.
-The small aerodynamic nose cone. Doubles as node occlusion for a fairing, but the required angle means it has less occlusion power. Very light but relatively low lift to drag compared to the above options, probably still a pretty good choice for this challenge.
-Fairings. This one's a free optimization because our existing crafts can easily be adapted to take advantage of this effect. It actually ends up hurting the partial run I did yesterday because the small magic wing effect is canceling out some of my wing lift.
-Flags. In 1.12 this is fixed, but in 1.11 (which I play for mostly unrelated reasons), flags are the most overpowered part in the game. They have incredibly high lift and also zero drag, meaning that your only source of drag will be the body drag from your hull. Additionally propellers with flags are extremely broken - I've created flag prop crafts with TWR of over 100 before, as well as pulling one all the way to Kerbin escape velocity while still in the atmosphere. Flags also make for great single-use landing gear and they're very light.

3 hours ago, swjr-swis said:

while your previous series of entries show the range growing exponentially at the blades moving inwards.

Actually I believe that my original entry also had offset blades by exactly the same amount. I just reduced mass and optimized the characteristics of the motors. 

[OJT]

2 hours ago, camacju said:

There's still plenty of funky aerodynamics stuff to work with. For example there's a few different types of parts that can be used as "Magic wings," basically parts that can produce a higher lift to drag ratio than any of KSP's normal wings:

-Heat shields. These are the "standard" magic wing parts, but they're quite heavy and our ultra-low-power props will probably have a hard time getting them up to speed.
-Landing gear. These are slightly lighter than heat shields but have a lower lift to drag ratio. Also you can land on them.
-The small aerodynamic nose cone. Doubles as node occlusion for a fairing, but the required angle means it has less occlusion power. Very light but relatively low lift to drag compared to the above options, probably still a pretty good choice for this challenge.
-Fairings. This one's a free optimization because our existing crafts can easily be adapted to take advantage of this effect. It actually ends up hurting the partial run I did yesterday because the small magic wing effect is canceling out some of my wing lift.
-Flags. In 1.12 this is fixed, but in 1.11 (which I play for mostly unrelated reasons), flags are the most overpowered part in the game. They have incredibly high lift and also zero drag, meaning that your only source of drag will be the body drag from your hull. Additionally propellers with flags are extremely broken - I've created flag prop crafts with TWR of over 100 before, as well as pulling one all the way to Kerbin escape velocity while still in the atmosphere. Flags also make for great single-use landing gear and they're very light.

Actually I believe that my original entry also had offset blades by exactly the same amount. I just reduced mass and optimized the characteristics of the motors. 

Yeah, I know about Magic Wings. But most Magic Wings from my knowledge are more applicable to supersonic and SSTO purposes, something that is outside of the scope of our challenge I think.  And I play on version 1.12 personally, so flags are out of the question for me.

Speaking of wings: from I gather, Magic Wings are mostly advantageous to get excellent Lift to Drag ratios for more efficient climbs. However, here we need to maintain lower altitudes to get better prop performance AND we need to maintain it stably so the plane doesn't do any corrections. For that no AoA seemed to be optimal setting for the wings. I did experiment with wing AoA and from the information I've found on the internet (KSP forum, reddit and Lt. Duckweed's wing video), 2° of AoA is the most optimal for low subsonic speeds, but the plane with 2° AoA not only flew slower, it also struggled more with take off. 

[swjr-swis]

2 hours ago, camacju said:

-Heat shields. These are the "standard" magic wing parts, but they're quite heavy

Not if you drain their ablator first. There's only one 'real' wing part lighter (basic fin) than a drained 0.625m heat shield, none of the control surfaces, and only the smallest of the prop and duct blades. Also makes it the cheapest and next-to-lightest separator/decoupler option, btw.

 

[camacju]

5 hours ago, swjr-swis said:

Not if you drain their ablator first. There's only one 'real' wing part lighter (basic fin) than a drained 0.625m heat shield, none of the control surfaces, and only the smallest of the prop and duct blades. Also makes it the cheapest and next-to-lightest separator/decoupler option, btw.

I was more talking about mass per effective wing area - a heat shield's wing area isn't very large.

Also if I remember correctly a 0.625m heat shield doesn't have an internal attachment node, which means it can't really be used as a magic wing.

5 hours ago, swjr-swis said:

Also makes it the cheapest and next-to-lightest separator/decoupler option, btw

0.625m heat shield with all ablator drained is 125 funds and 25 kg. The small hardpoint is 60 funds and the structural pylon is 125 funds, both of which have the advantage of being radial attachable. The 0.625m decoupler and separator are 10 kg, the small docking port is 20 kg, and the TT-38K radial decoupler is 25 kg. 

5 hours ago, OJT said:

Speaking of wings: from I gather, Magic Wings are mostly advantageous to get excellent Lift to Drag ratios for more efficient climbs. However, here we need to maintain lower altitudes to get better prop performance AND we need to maintain it stably so the plane doesn't do any corrections. For that no AoA seemed to be optimal setting for the wings. I did experiment with wing AoA and from the information I've found on the internet (KSP forum, reddit and Lt. Duckweed's wing video), 2° of AoA is the most optimal for low subsonic speeds, but the plane with 2° AoA not only flew slower, it also struggled more with take off. 

Lift to drag ratio is also very important for range. If you have a higher L/D, you can achieve the same lift for less drag. This means if you are flying at the same speed and altitude, you need less thrust to maintain level flight. This would mean less prop torque = less electricity usage.

KSP wings are symmetric - zero AoA means zero lift. If you go into AeroGUI it should tell you your actual AoA. If 2 degrees wing incidence is making you struggle and fly slower, that means your wing area is too high - it'll produce more lift but also more drag - so you should reduce your wing. It'll help reduce mass also.

5 hours ago, OJT said:

But most Magic Wings from my knowledge are more applicable to supersonic and SSTO purposes, something that is outside of the scope of our challenge I think. 

Not at all - the idea is that they provide a superior lift to drag ratio in all flight regimes. It's just that they take less of a penalty from Mach effects, so their relative advantage over standard wings is magnified when at supersonic speeds.

Edited May 19, 2022 by camacju

[18Watt]

On 5/18/2022 at 10:22 AM, OJT said:

At this point, what constitutes a "legal" and "illegal" exploit?

I've been busy at work the past week or so, but have been thinking about this.  I haven't really come up with an answer, at least not a good one!  The rules (so far) essentially allow you to place stock parts anywhere you want.  That was my original intention, to find out what can be accomplished with stock parts, and few, if any, further limitations.

I think you, @camacju, and @swjr-swis have discovered that there is indeed a way to keep two Kerbals airborne indefinitely using the props.  I really do not want to place an arbitrary limitation of not off-setting the prop blades, because KSP will allow you to do this.  Sadly, that does cause problems for this challenge.

On 5/18/2022 at 10:28 AM, camacju said:

You've touched on the main reason why it's so hard to determine what counts as cheaty in KSP. Everyone has a different threshold for what mechanics they'll be willing to abuse, whether it be part clipping, root fairing body craft, magic wings, or even Kraken drives.

Yes, again the original rules of this challenge were that you can place stock parts anywhere KSP will allow.  I really do not want to adjust that rule, even though it may cause this particular challenge to be more or less complete.

On 5/18/2022 at 5:47 PM, OJT said:

2° of AoA is the most optimal for low subsonic speeds, but the plane with 2° AoA not only flew slower, it also struggled more with take off. 

I used to be a non-believer regarding AOA, partly because I hadn't figured out how to do it in less than 5 degree increments.  For SSTOs 5 degrees is way too much.  I eventually came around, and also find 1-2 degrees helpful, even for SSTOs.  One big advantage is I can lock to pro-grade, and still fly a gentle climb, which is helpful when not using any autopilots.

OK!  Not being sure what to do with this challenge at this point, if any of you have suggestions let me know.  Personally, I think the best route would be to close this challenge, and create a new one if there is any interest, perhaps specifying offset rules.

Also, I've been away at work for about a week, so if I missed any entries that need to go on the leaderboard, please let me know!  Many thanks to everyone who has participated!

 

[camacju]

18 minutes ago, 18Watt said:

For SSTOs 5 degrees is way too much.

You may be using too much wing area then. 5 degrees is close to the optimal value for SSTO craft (I think 4 degrees is slightly better but it's pretty close). Maybe you're used to low wing incidence requiring more actual wing area so when you rotate your wings upward you get a lot of drag.

I like to aim for at least 6 tons per wing area, which leads to quite small wings for the plane's size but the increased lift from the wings makes up for that.

[18Watt]

1 minute ago, camacju said:

You may be using too much wing area then.

Yes, that is almost certainly the case.  One thing I like to achieve with my SSTOs is a fairly low takeoff speed, even when fully loaded.  My SSTOs usually are capable of lifting off at 80-90 m/s, generally with at least 1/3 of the runway remaining.

Why?  One reason is just personal preference.  But I do have a practical reason as well.  There is usually the possibility that I’ll eventually want to take the SSTO to Laythe.  It’s hard to find a long flat surface on Laythe, so the ability to use less runway, and get flying at lower speeds is helpful.

But that does mean I end up with a lot more wing area than what is optimal.  I think optimal would be a ship that can just barely stay in the air when reaching the end of the runway.  The runway is several meters above sea-level, so even a slight descent to build flying speed works if needed.

In the back of my mind I also think about abort scenarios where I lose an engine during takeoff.  Stock KSP does not present that situation, but I still plan for it anyway.

I don’t remember what ratio of mass to wing I usually use, but it is far less than 6 tons per wing.   With the low wing loading I use, anything more than 2-3 degrees incidence actually causes increased drag, because I’m actually pointed well below prograde to maintain my desired flight path.  Now the fuselage is producing negative lift, along with the drag.  At high altitudes that becomes less of a factor, but still limits the speed I can reach on jet power.

[OJT]

Reviving the thread... with first completed circumnavigation!

Plane like in previous entry, but with slight drag adjustments and offset fan blades. I didn't offset them far though, enough to make them look aesthetically pleasant

EC charge proof

Flying first eastward towards the peninsula. I found out through testing that, if you keep RPMs low and fly the plane as stable as possible, you can reliably fly with phys timewarp engaged. The whole flight was done with 3x time warp (with occasional boosts to 4x)

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From that point, I was following the geodesic

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Returning to peninsula checkpoint

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Catching the transit of Minmus across the Sun

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Passing between two islands for the second time

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Out of charge, gliding down

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Splashdown

Coordinates of splashdown and all the checkpoint flags

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Calculating distance (using the website from previous entries for some of these):

• From KSC to Checkpoint 1 at peninsula - 369.16 km
• One full circumnavigation - 3769.9 km (I assume the equatorial circumference despite not traveling along the equator, since KSP doesn't simulate planetary flattening)
• From Checkpoint 1 to water passage between islands near Checkpoint 2 - 639.9 km
• From water passage to splashdown site - 144 km

And the total distance is... 4922.96 km

Even with 3x time warp, the flight took up almost 6 hours. Without it, it'd take up 17 hours. Managing a stable flight with phys warp is the only reason I decided to go ahead with the flight

[camacju]

I suspect a single motor design will inherently be better for this, because it allows your electricity usage to go just a little bit lower without rounding down to zero. Apparently, if a motor is consuming less than 0.001 u/s, KSP simply thinks it's not consuming any power at all, despite still outputting torque. So in my earlier aborted attempt, I had two motors each consuming 1.04 mu/s, just above the threshold. The craft could actually still fly on slightly lower throttle, but KSP would just set electricity consumption to exactly zero. Meanwhile @OJT has one motor drawing 1.57 mu/s, which is significantly lower total power draw, and can likely go even lower.

17 hours ago, OJT said:

Plane like in previous entry, but with slight drag adjustments and offset fan blades. I didn't offset them far though, enough to make them look aesthetically pleasant

Have you tried using fewer blades? I found that two blades per prop worked just fine - the blades need to each contribute more thrust, but you will have lower mass and drag to make up for it.

Also you don't need the 1K battery pack - the 1.25m aerodynamic nose cone works just fine to occlude and you save mass by using that plus a Z-100 battery.